Which of the following compounds is highly soluble in water ?

Options

A. `CaF_(2)`
B. `MgF_(2)`
C. `BeF_(2)`
D. `BaF_(2)`

Answer

C

Explanation

Owing to the high hydration energy of `Be^(2+)` `(-2494kJmol^(-1))` in forming `[Be(H_(2)O)_(4)]^(2+)` beryllium fluoride is very soluble in water. All the other fluorides, `MF_(2)` which are ionic are almost insoluble in water as their as their hydration enthalpies are not able to outweigh their lattice enthalpies. Howerver,
The solubility increases slightly with increase in cation size due to the decrease of charge density.